Terraform Regex Patterns Skill

Overview

This skill provides a curated set of regular expression (regex) patterns and usage examples for use with Terraform's built-in regex functions:

• •regex(pattern, string)
• •regexall(pattern, string)
• •replace(string, substring/pattern, replacement)

It also covers syntax, sequences, and flags as documented in the Terraform regex function documentation.

Syntax and Flags

Terraform uses RE2 syntax. Flags are set inline in the pattern, e.g. (?i) for case-insensitive.

Sequences

Flags

Some of the matching behaviors described above can be modified by setting matching flags, activated using either the (?flags) operator (to activate within the current sub-pattern) or the (?flags:x) operator (to match x with the modified flags). Each flag is a single letter, and multiple flags can be set at once by listing multiple letters in the flags position. The available flags are listed in the table below:

| Flag | Meaning | | i | Case insensitive: a literal letter in the pattern matches both lowercase and uppercase versions of that letter | | m | The ^ and $ operators also match the beginning and end of lines within the string, marked by newline characters; behavior of \A and \z is unchanged | | s | The . operator also matches newline | | U | The meaning of presence or absense ? after a repetition operator is inverted. For example, x* is interpreted like x*? and vice-versa. |

Usage Examples

Validate Email Address

regex("^[\w._%+-]+@[\w.-]+\\.[a-zA-Z]{2,}$", var.email)

Extract Digits from String

regexall("\\d+", var.input)

Replace All Whitespace with Dash

replace(var.input, "\\s+", "-")

Match AWS ARN

regex("^arn:aws:[a-z0-9-]+:[a-z0-9-]*:[0-9]*:.*$", var.arn)

Case-Insensitive Match

regex("(?i)^prod$", var.env)

Extract Lowercase Letters from String

regex("[a-z]+", "53453453.345345aaabbbccc23454")
# returns: aaabbbccc

Extract Date Parts from String

regexall("\\d+", "2019-02-01")
# returns: ["2019", "02", "01"]

Parse URL Scheme and Authority

regex("^(?:(?P<scheme>[^:/?#]+):)?(?://(?P<authority>[^/?#]*))?", "https://terraform.io/docs/")
# returns: { "authority" = "terraform.io", "scheme" = "https" }

Error: Pattern Did Not Match

regex("[a-z]+", "53453453.34534523454")
# error: pattern did not match any part of the given string

Pattern Library

References

• •Terraform regex function
• •RE2 syntax

How to Use

• •Use these patterns directly in regex, regexall, or replace functions in Terraform.
• •Adjust patterns as needed for your use case.
• •For complex validation, combine multiple patterns or use regexall for all matches.